Summer must be brewing because it’s free iced coffee day at Dunkin' Donuts. Well, some Dunkin' locations. Er, actually, only participating locations in 13 of the hundreds of cities that Dunkin' Donuts serves are giving away the stuff.

Apparently, when word leaked out over the Internet that some locations but not others were offering the free product, some people got angry at the Massachusetts-based chain. Customers from Maine to North Carolina were posting messages Tuesday on Dunkin’s Facebook page complaining about the lack of free coffee in their town.

“Yea, y [sic] state something and then not follow through with it entirely?? What kind of business is that??” writes one customer. Fighting words from another: “DD needs to get their act together or people are going to boycott.”

So why free java for a select few? A Dunkin' Donuts spokesperson explained via e-mail that: "As part of our 60th birthday celebration, Dunkin’ Donuts is offering a variety of regional promotions throughout the year rather than a national Free Iced Coffee Day."

Technically, customers don’t need to live near one of the special 13 locations to score a free beverage. Last week Dunkin' Donuts started offering select beverages gratis to customers who registered for its Dunkin' Perks program online. Just surrender your name, address, date of birth, and e-mail, and a coupon for a drink of your choosing will make its way to you.

But that's not exactly free, is it?

Just like Mama said, there’s no such thing as a free lunch. Or beverage.